Those are not light bullets LOL.
BTW the PPSh 41 weights in at 10.5 lbs unloaded.
Thompson was also about 10 lbs unloaded. Then add 50 each 230 grain round nose....
I ran a M-3 greasegun range at Graf once. 90 round familiarization course. Three 32 round magazines in a carrier were enough to bend your pistol belt over.
Very important to impress upon people to keep their guns up and down range at all times. Grease guns don’t have much of a safety, just a little metal flap that pokes into a hole in the bolt, maybe.
What you really want to avoid is having the shooter do is turn from facing down range with his smg, then turn toward his next station, sweeping all the people on the other stations as he walks toward it. Our ammunition was nearly all about to expire (WWII rounds laid down in 1944!).
When it comes down to it, best to have him remove the magazine, and lock the bolt back, and have is coach inspect to be sure it is clear.
Ah! the joys of the Carter Administration!